Generators supply vital power for base buildings and turrets in Firestrike.
A few players have asked about the reasons for the specific stats and levels on Generators. Here is the answer from the design team:
Each Tactical Ops Center (TOC) level unlocks a certain number of Generators, and allows them to be upgraded to a certain level limit. For example, TOC Level 9 allows 3 Generators of up to Level 9 each. The power stats of Generators are designed so that, for each TOC level, a fully-upgraded set of Generators provides just enough juice to power a maxed-out base with all the buildings built and upgraded to the limit for that TOC level. As long as you keep upgrading your Generators along with your other buildings, you should never need to run out of power.